Interpreting 2hJ(F,N), 1hJ(H,N) and 1J(F,H) in the hydrogen-bonded FH–collidine complex

✍ Scribed by Janet E. Del Bene; Rodney J. Bartlett; José Elguero

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 133 KB
• Volume: 40
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1103

✦ Synopsis

Abstract

Ab initio EOM‐CCSD calculations were performed to determine ^19^F,^1^H, ^19^F,^15^N and ^1^H,^15^N spin–spin coupling constants in model complexes FH–NH~3~ and FH–pyridine as a function of the F—H and F—N distances. The absolute value of ^1^J(F,H) decreases and that of ^1h^J(H,N) increases rapidly along the proton‐transfer coordinate, even in the region of the proton‐shared F—H—N hydrogen bond. In contrast, ^2h^J(F,N) remains essentially constant in this region. These results are consistent with the recently reported experimental NMR spectra of FH–collidine which show that ^1h^J(H,N) increases and ^1^J(F,H) decreases, while ^2h^J(F,N) remains constant as the temperature of the solution decreases. They suggest that the FH–collidine complex is stabilized by a proton‐shared hydrogen bond over the range of experimental temperatures investigated, being on the traditional side of quasi‐symmetric at high temperatures, and on the ion‐pair side at low temperatures. Copyright © 2002 John Wiley & Sons, Ltd.